US6360264B1 - Method and apparatus for maintaining connectivity of nodes in a wireless local area network - Google Patents

Method and apparatus for maintaining connectivity of nodes in a wireless local area network Download PDF

Info

Publication number
US6360264B1
US6360264B1 US08/537,408 US53740895A US6360264B1 US 6360264 B1 US6360264 B1 US 6360264B1 US 53740895 A US53740895 A US 53740895A US 6360264 B1 US6360264 B1 US 6360264B1
Authority
US
United States
Prior art keywords
access point
node
handoff
set forth
request
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime, expires
Application number
US08/537,408
Inventor
Raphael Rom
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sun Microsystems Inc
Original Assignee
Sun Microsystems Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sun Microsystems Inc filed Critical Sun Microsystems Inc
Priority to US08/537,408 priority Critical patent/US6360264B1/en
Application granted granted Critical
Publication of US6360264B1 publication Critical patent/US6360264B1/en
Adjusted expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W36/00Hand-off or reselection arrangements
    • H04W36/0005Control or signalling for completing the hand-off
    • H04W36/0055Transmission or use of information for re-establishing the radio link
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W36/00Hand-off or reselection arrangements
    • H04W36/0005Control or signalling for completing the hand-off
    • H04W36/0083Determination of parameters used for hand-off, e.g. generation or modification of neighbour cell lists
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W36/00Hand-off or reselection arrangements
    • H04W36/08Reselecting an access point
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W84/00Network topologies
    • H04W84/02Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
    • H04W84/10Small scale networks; Flat hierarchical networks
    • H04W84/12WLAN [Wireless Local Area Networks]
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W48/00Access restriction; Network selection; Access point selection
    • H04W48/20Selecting an access point
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W88/00Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
    • H04W88/08Access point devices
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W92/00Interfaces specially adapted for wireless communication networks
    • H04W92/16Interfaces between hierarchically similar devices
    • H04W92/20Interfaces between hierarchically similar devices between access points

Definitions

  • the present invention relates to the field of wireless local area networks (LANs) and, more particularly, to a method and apparatus for maintaining connectivity of nodes in a wireless LAN.
  • LANs wireless local area networks
  • the nodes in a wired network communicate with each other by using transmission lines to carry the signals between the nodes.
  • the nodes in a wireless network communicate with each other using radio signals or other types of wireless links rather than physical interconnections.
  • a wireless local area network is local in the sense that the transceiver nodes are located within a radius of only a few miles of each other. As such, the proximity of the nodes permits the network to operate reliably at low power and at high data rates.
  • nodes in a wireless LAN are mobile and transmit information in packets. These nodes, although mobile, may be geographically grouped at any given time into basic service areas (BSAs), otherwise referred to as “cells.”
  • BSAs basic service areas
  • the nodes within a cell communicate with each other either directly or through a cell coordinator that relays messages among the nodes of the cell.
  • the coordinator itself may be implemented either within a regular node or in a node that only performs the coordination function.
  • AP access point
  • each cell must contain at least one AP.
  • the coordinator and the AP are often implemented in the same node. Communication among the APs may take place over the same or different radio channels or via a separate wired network.
  • each node is associated with a coordinator in a cell (if one exists), and in a multi-cell system each node is also associated with at least one AP in a cell.
  • the association of a node with a particular AP may be based on criteria such as the quality of the link between the node and the AP, and the load carried by the AP.
  • the self-organization procedure is considered complete when a node has acquired the parameters that will enable it to effectively communicate within the cell with peer nodes or relay points.
  • the network must be reconfigured to maintain connectivity between communicating nodes.
  • This reconfiguration or topological change requires the reassociation of a node with another coordinator or another AP or both.
  • the process of ceasing communications between a node and a coordinator or between a node and an access point and reassociating the node with another coordinator or access point is known as “handoff”.
  • a handoff is typically required when a node has moved away from one AP towards another, either within a cell or across cells.
  • Network reconfiguration may also arise as a result of a change in the quality of reception between a node and an AP, or because an AP has become overloaded.
  • the handoff process is controlled solely by the base stations (corresponding to APs). Because the node does not participate at all (or participates only minimally) in the handoff process, cellular telephone systems require a considerable amount of cooperation among the base stations. This cooperation entails identifying those base stations that are in radio contact with the node as well as determining the most suitable new base stations.
  • radio links are asymmetric, and the signal characteristics transmitted are not necessarily the same as those received.
  • a base station cannot determine how well a node receives a signal transmitted by the base station based upon how well the base station receives a signal from the node. This phenomenon makes the base station selection even more complex.
  • any messages destined for the node must be rerouted to the new base station.
  • each node can conduct only one conversation at a time with another node in the network.
  • a conversation is routed through a series of switches located between the two nodes at the ends of the communication path.
  • the path must be reconfigured, usually requiring that the message pass through a path consisting of a different set of switches.
  • a node in a computer network communicates at high data rates and has the capability to carry on multiple conversations simultaneously with other nodes.
  • the nodes in a computer network typically communicate via packets, wherein each packet may represent a portion of a conversation, and each such packet can be interleaved in any manner with other packets that contain portions of other conversations. Because of the large number of conversations carried on by a node, reconfiguration of all of the communication paths carrying those conversations is understandably a very complex process.
  • computers communicate in this manner renders the technique used by cellular telephone systems inadequate to accomplish the handoff of a computer node because of the inordinate amount of time that would be required to reconfigure the entire communication path to reroute all of these conversations.
  • LAN wireless local area network
  • the present invention provides a method and apparatus for maintaining connectivity in a wireless LAN.
  • the LAN is divided into a plurality of cells. Each cell is occupied by at least one access point for communicating information between the cells, and at least one node for communicating via the LAN through the access points.
  • the node To initiate a handoff from a first access point with which the node is currently communicating, the node first selects a second access point as a candidate for handoff. The node then communicates an instruction to the first access point instructing the first access point to relay a request to the second access point that the second access point accept a handoff of the node from the first access point. The first access point then relays the request directly to the second access point. In response, the second access point transmits its operating parameters to the node through the first access point, and the node adjusts its own parameters in response so as to establish communication between the node and the second access point, thereby accomplishing handoff.
  • FIG. 1 is an illustration of a wireless LAN.
  • FIGS. 2A and 2B illustrate the handoff of a node in a wireless LAN.
  • FIG. 3A is a flow chart illustrating the method of the present invention.
  • FIGS. 3B-3F are more detailed illustrations of the steps of FIG. 3 A.
  • FIG. 4 illustrates the reconfiguration of a prior art cellular network telephone after handoff.
  • FIG. 5 illustrates the reconfiguration of a wireless LAN after handoff according to the present invention.
  • FIG. 6 illustrates an apparatus implementing the present invention.
  • FIG. 7 illustrates a packet containing access point operating parameters.
  • FIG. 8 illustrates a microprocessor-based transceiver that can be used to implement the nodes and access points of the present invention.
  • the present invention provides a method and apparatus for maintaining connectivity of nodes in a wireless LAN. Unlike prior art systems, in the present invention the node participates in the decision as to whether it will be handed off and, if so, to which access point. Moreover, the invention applies not only to a node maintaining a single conversation, but it also supports multiplexed communication among nodes operating at high data rates in a packet switching environment.
  • FIG. 1 illustrates a typical wireless LAN.
  • Nodes 10 are organized into geographic regions called “basic service areas” (BSAs) or “cells” 11 . Note that a node can belong to more than one cell.
  • the nodes within a cell communicate with each other either directly or through a coordinator 12 , which relays messages among the nodes of the cell.
  • a node within one cell cannot communicate directly with a node in another cell. Rather, the message must be relayed through a series of access points (APs) 13 , which are linked together either through a separate radio channel or a wired network 14 .
  • APs access points
  • Each cell contains at most one coordinator and at least one access point, and each node within a cell is associated with at most one coordinator and at least one access point.
  • the functionality of the coordinator and the access point may be combined in a single device 15 .
  • more than one node may be associated with a given AP. For example, two nodes 10 are associated with AP 13 , as indicated by the dotted lines.
  • the determination of which AP is to be associated with a particular node is based upon criteria such as the quality of the signal transmitted between the node and the AP, and the load carried by the AP.
  • This process of associating a node with an AP is known as “self-organization,” and is well known in the art.
  • the invention utilizes the self-organization process described in copending U.S. patent application Ser. No. 07/915,433, filed Jul. 17, 1992, titled “METHOD AND APPARATUS FOR IMPLEMENTING SELF-ORGANIZATION IN A WIRELESS LOCAL AREA NETWORK.”
  • FIGS. 2A and 2B generally illustrate the handoff process in a wireless LAN.
  • FIGS. 2A and 2B show a node 20 traveling from one BSA to another. Initially, node 20 is associated with an access point 21 . As node 20 moves away from AP 21 and towards AP 22 , the quality of the radio link between AP 21 and node 20 deteriorates. Thus, it is desirable to sever the link between node 20 and AP 21 , and reassociate node 20 with an AP that would offer a higher quality of message transmission to node 20 .
  • node 20 As node 20 approaches the cell occupied by access point 22 , AP 22 becomes a potential candidate for reassociation because it is now closer to node 20 , and thus is likely to offer a better communications link to the node. Therefore, node 20 is handed off to AP 22 , as shown in FIG. 2 B.
  • FIG. 3A is a flow chart illustrating the method of the present invention.
  • the flowchart steps are annotated with the names of the components (shown in FIG. 6) that perform the diagrammed steps.
  • the node first determines whether handoff is necessary, as shown in step 30 and further illustrated as step 74 in FIG. 3 B.
  • the node may measure the quality of the signal received from the access point with which it is communicating, and determine that handoff is necessary when received signal quality drops below a predetermined threshold.
  • the determination by the node of whether a handoff is necessary may be made in response to a request from the access point with which the node is currently communicating, as shown in FIG. 3 C.
  • the current access point communicates a request to the node that it initiate the reassociation process in order to be handed off to another access point, step 37 .
  • the node has the option of accepting or rejecting this request, step 38 .
  • the determination of whether handoff is necessary may be made solely by the current access point.
  • the node When handoff is deemed necessary, acquires parameters from other access points. These parameters may include, for example, information concerning administrative domain and access point load. (The administrative domain represents the particular authority which operates a given access point.) Based upon this information and the quality of the signals received from the other access points, the node determines an AP to select for reassociation, step 31 .
  • the selection of the new access point by the node represents a significant advantage over prior art systems in which the node does not actively participate in the reassociation process.
  • the access points must determine, through communications among themselves, which AP will be associated with the node for handoff, using such criteria as which AP receives the highest quality signal from the node.
  • the node due to the asymmetric nature of radio links, the node itself can best determine the quality of the signal received at the node.
  • the present invention achieves a substantial improvement in the quality of the node-access point association.
  • the node After selecting a new access point, the node communicates an instruction to the current access point instructing it to relay a message to the selected access point, requesting that the selected access point accept the handoff of the node, step 32 .
  • This request is relayed to the selected access point by the current access point, along with a transfer of certain node parameters representing characteristics of the node, step 33 .
  • These node parameters may include, for example, an identification of the user occupying the node.
  • the selected access point responds automatically to the node's request by transferring a packet containing its operating parameters to the node through the old access point.
  • the operating parameters typically include, but are not limited to, the frequency of the channel on which the selected access point communicates with nodes, spreading codes (in spread spectrum systems) and data encryption information required to access the selected access point.
  • a typical packet is illustrated in FIG. 7 .
  • the node Based upon these access point parameters, the node adjusts its own parameters and commences communication with the new access point, thereby accomplishing handoff, step 35 . The process is further illustrated in steps 90 , 92 and 94 of FIG. 3 D.
  • the selected access point does not automatically transfer its operating parameters in response to the request of the node. Rather, the selected access point determines whether to accept the handoff based upon predetermined criteria, including the node parameters, step 34 . For example, the selected access point may examine whether its load is light enough to accommodate communication with another node, whether the quality of the signal received from the node is satisfactory, and whether the identification of the node reveals that it is authorized to communicate with the selected access point. If the selected access point accepts the handoff, then it transmits its operating parameters to the node through the old AP, so that handoff may be accomplished, step 35 .
  • the selected access point rejects the request of the node, then the node repeats the reassociation process, steps 31 , 32 , 33 , 34 , to select a different access point with which to establish communications.
  • the present invention avoids this degree of complexity. This is illustrated by FIG. 5 . Instead of reconfiguring in advance every point throughout the path, the communication path remains intact except that the message is now forwarded from the old access point 61 to the new access point 62 . For example, when a message intended for the node 60 is received at access point 61 , AP 61 forwards the message to the new access point 62 . In this manner, the invention establishes connectivity of the node with network through the second access point, step 36 further illustrated as step 70 in FIG. 3 E).
  • the old access point 61 may inform other nodes and access points that node 60 is now associated with new access point 62 , thus allowing the other access points to adjust their parameters and communicate directly with access point 62 (step 36 , further illustrated as step 72 in FIG. 3 F).
  • This process of informing other nodes and access points may be performed at a time convenient to do so, i.e., when there is a break in communications and need not be done immediately.
  • the present invention achieves a significant advantage over conventional systems.
  • the conventional method is too slow to accommodate the handoff of a node that may be engaged in multiple conversations with other nodes.
  • the manner in which the present invention establishes connectivity between the node through the new access point and the rest of the network is much simpler and faster than the full scale reconfiguration required by conventional means.
  • FIG. 6 is a simplified block diagram of a node 70 and two access points 74 and 78 , which may be used to implement the present invention.
  • Each node 70 includes a node processing unit 71 which communicates with a device 72 and is connected to an antenna 73 to permit communication between the node and the network.
  • the device 72 represents any apparatus that occupies a node, e.g., a computer, a peripheral device or communications hardware.
  • Access point 74 includes an AP processing unit 75 , which is linked to antenna 76 to allow AP 74 to communicate with node 70 and other nodes in the network.
  • AP link 77 which may be implemented as a radio transceiver or as an interface to a separate wired network of access points.
  • Access point 74 is connected to other access points, such as access point 78 .
  • Access point 78 like access point 74 , includes an AP processing unit 79 connected to AP link 77 and an antenna 80 .
  • the node processing unit 71 through antenna 73 , communicates via radio with first access point processing unit 75 through antenna 76 .
  • the node processing unit 71 may decide that the node 70 should establish communications with another access point if, for example, the quality of signal received by the node processing 71 from the first access point 74 falls below a predetermined signal quality threshold, or if the traffic load being carried by the first access point processing unit 75 exceeds a predetermined load threshold.
  • the node processing unit 71 acquires parameters from other access points. For example, second access point processing unit 79 , through antenna 80 , may transmit information regarding administrative domain and access point load. Based upon this information and the quality of the signals received from the other access points, the node processing unit 71 selects an AP, such as second access point 78 , for reassociation.
  • an AP such as second access point 78
  • the node processing unit 71 After selecting an AP, the node processing unit 71 communicates an instruction to first access point processing unit 75 to relay a request over AP link 77 to second access point processing unit 79 , requesting that second access point 78 accept a handoff of the node 70 .
  • the request is relayed to second access point processing unit 79 along with a transfer of certain node parameters representing characteristics of the node 70 .
  • the AP processing unit 79 determines whether to accept the handoff. If so, then through AP link 77 , second access point processing unit 79 transmits operating parameters across AP link 77 to first access point processing unit 75 to be relayed to the node 70 .
  • the node processing unit 71 adjusts the operating parameters of the node so that it can communicate across a radio link through antennas 73 and 80 to the second access point processing unit 79 , thereby accomplishing handoff.
  • the first access point processing unit 75 forwards messages intended for node 70 across AP link 77 to the second access point processing unit 79 upon receipt of those messages at the first access point 74 .
  • the first access point processing unit 75 may inform other access points over AP link 77 that node 70 is now associated with second access point 78 , thus allowing the other access points to communicate directly with access point 78 .

Abstract

Methods and apparatus for maintaining connectivity of nodes in a wireless LAN. Accordingly, the present invention provides a method and apparatus for maintaining connectivity in a wireless LAN. The LAN is divided into a plurality of cells. Each cell is occupied by at least one access point for communicating information between the cells, and at least one node for communicating via the LAN through the access points. To initiate a handoff from a first access point with which the node is currently communicating, the node first selects a second access point as a candidate for handoff. The node then communicates an instruction to the first access point instructing the first access point to relay a request to the second access point that the second access point accept a handoff of the node from the first access point. The first access point then relays the request to the second access point. In response, the second access point transmits its operating parameters to the node through the first access point, and the node adjusts its own parameters in response so as to establish communication between the node and the second access point, thereby accomplishing a handoff.

Description

This is a continuation of application Ser. No. 08/316,078 filed Sep. 30, 1994 now abandoned, which is a continuation of application Ser. No. 07/941,735 filed Sep. 8, 1992 now abandoned.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of wireless local area networks (LANs) and, more particularly, to a method and apparatus for maintaining connectivity of nodes in a wireless LAN.
2. Description of the Related Art
Through the merging of computer and communications technology, computer networks have greatly enhanced the computing power available to the individual computer user linked to other computers in a network. Not only do networks provide for the exchange of information between autonomous computers, but they also enable each user or “node” to share resources common to the entire network. Through resource sharing, all application programs, data bases and physical equipment in the network may be made available to any node without regard to the physical location of the resource or the user.
As for the linkage between nodes, there are generally two types of network interconnections. The nodes in a wired network communicate with each other by using transmission lines to carry the signals between the nodes. The nodes in a wireless network, on the other hand, communicate with each other using radio signals or other types of wireless links rather than physical interconnections.
One type of wireless network is a wireless local area network (LAN). A LAN is local in the sense that the transceiver nodes are located within a radius of only a few miles of each other. As such, the proximity of the nodes permits the network to operate reliably at low power and at high data rates.
Typically, nodes in a wireless LAN are mobile and transmit information in packets. These nodes, although mobile, may be geographically grouped at any given time into basic service areas (BSAs), otherwise referred to as “cells.” The nodes within a cell communicate with each other either directly or through a cell coordinator that relays messages among the nodes of the cell. The coordinator itself may be implemented either within a regular node or in a node that only performs the coordination function.
Communication between nodes in different BSAs is accomplished through an access point (AP), which is responsible for relaying packets into and out of the BSA. To allow for inter-cell communication, each cell must contain at least one AP. The coordinator and the AP are often implemented in the same node. Communication among the APs may take place over the same or different radio channels or via a separate wired network.
During node power-up, the node is assimilated into the network environment using what is known as the network “self-organization” capability. During self-organization, each node is associated with a coordinator in a cell (if one exists), and in a multi-cell system each node is also associated with at least one AP in a cell. The association of a node with a particular AP may be based on criteria such as the quality of the link between the node and the AP, and the load carried by the AP. The self-organization procedure is considered complete when a node has acquired the parameters that will enable it to effectively communicate within the cell with peer nodes or relay points.
As conditions in the network environment vary, the network must be reconfigured to maintain connectivity between communicating nodes. This reconfiguration or topological change requires the reassociation of a node with another coordinator or another AP or both. The process of ceasing communications between a node and a coordinator or between a node and an access point and reassociating the node with another coordinator or access point is known as “handoff”. In a mobile telecommunications system, a handoff is typically required when a node has moved away from one AP towards another, either within a cell or across cells. Network reconfiguration may also arise as a result of a change in the quality of reception between a node and an AP, or because an AP has become overloaded.
In conventional cellular telephone systems, the handoff process is controlled solely by the base stations (corresponding to APs). Because the node does not participate at all (or participates only minimally) in the handoff process, cellular telephone systems require a considerable amount of cooperation among the base stations. This cooperation entails identifying those base stations that are in radio contact with the node as well as determining the most suitable new base stations. However, radio links are asymmetric, and the signal characteristics transmitted are not necessarily the same as those received. Thus, a base station cannot determine how well a node receives a signal transmitted by the base station based upon how well the base station receives a signal from the node. This phenomenon makes the base station selection even more complex.
Once the system is reconfigured, any messages destined for the node must be rerouted to the new base station. In a cellular telephone system, each node can conduct only one conversation at a time with another node in the network. In such a system, a conversation is routed through a series of switches located between the two nodes at the ends of the communication path. When one of those nodes is handed off to another base station, the path must be reconfigured, usually requiring that the message pass through a path consisting of a different set of switches.
Because each telephone in a cellular telephone system carries on only one conversation at a time, it is a relatively simple matter to reconfigure the entire communication path to hand off the telephone conversation. However, unlike a telephone unit in a cellular system, a node in a computer network communicates at high data rates and has the capability to carry on multiple conversations simultaneously with other nodes. The nodes in a computer network typically communicate via packets, wherein each packet may represent a portion of a conversation, and each such packet can be interleaved in any manner with other packets that contain portions of other conversations. Because of the large number of conversations carried on by a node, reconfiguration of all of the communication paths carrying those conversations is understandably a very complex process. Moreover, the fact that computers communicate in this manner renders the technique used by cellular telephone systems inadequate to accomplish the handoff of a computer node because of the inordinate amount of time that would be required to reconfigure the entire communication path to reroute all of these conversations.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a wireless local area network (LAN) in which the node participates in the coordination of the handoff process.
It is a further object of the invention to provide a wireless LAN in which connectivity is maintained among users carrying on multiple conversations at high data rates.
Accordingly, the present invention provides a method and apparatus for maintaining connectivity in a wireless LAN. The LAN is divided into a plurality of cells. Each cell is occupied by at least one access point for communicating information between the cells, and at least one node for communicating via the LAN through the access points.
To initiate a handoff from a first access point with which the node is currently communicating, the node first selects a second access point as a candidate for handoff. The node then communicates an instruction to the first access point instructing the first access point to relay a request to the second access point that the second access point accept a handoff of the node from the first access point. The first access point then relays the request directly to the second access point. In response, the second access point transmits its operating parameters to the node through the first access point, and the node adjusts its own parameters in response so as to establish communication between the node and the second access point, thereby accomplishing handoff.
BRIEF DESCRIPTION OF THE DRAWINGS
The objects, features and advantages of the present invention will be apparent to one skilled in the art in light of the following detailed description in which:
FIG. 1 is an illustration of a wireless LAN.
FIGS. 2A and 2B illustrate the handoff of a node in a wireless LAN.
FIG. 3A is a flow chart illustrating the method of the present invention;
FIGS. 3B-3F are more detailed illustrations of the steps of FIG. 3A.
FIG. 4 illustrates the reconfiguration of a prior art cellular network telephone after handoff.
FIG. 5 illustrates the reconfiguration of a wireless LAN after handoff according to the present invention.
FIG. 6 illustrates an apparatus implementing the present invention.
FIG. 7 illustrates a packet containing access point operating parameters.
FIG. 8 illustrates a microprocessor-based transceiver that can be used to implement the nodes and access points of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a method and apparatus for maintaining connectivity of nodes in a wireless LAN. Unlike prior art systems, in the present invention the node participates in the decision as to whether it will be handed off and, if so, to which access point. Moreover, the invention applies not only to a node maintaining a single conversation, but it also supports multiplexed communication among nodes operating at high data rates in a packet switching environment.
FIG. 1 illustrates a typical wireless LAN. Nodes 10 are organized into geographic regions called “basic service areas” (BSAs) or “cells” 11. Note that a node can belong to more than one cell. The nodes within a cell communicate with each other either directly or through a coordinator 12, which relays messages among the nodes of the cell.
A node within one cell cannot communicate directly with a node in another cell. Rather, the message must be relayed through a series of access points (APs) 13, which are linked together either through a separate radio channel or a wired network 14.
Each cell contains at most one coordinator and at least one access point, and each node within a cell is associated with at most one coordinator and at least one access point. The functionality of the coordinator and the access point may be combined in a single device 15. In addition, more than one node may be associated with a given AP. For example, two nodes 10 are associated with AP 13, as indicated by the dotted lines.
The determination of which AP is to be associated with a particular node is based upon criteria such as the quality of the signal transmitted between the node and the AP, and the load carried by the AP. This process of associating a node with an AP is known as “self-organization,” and is well known in the art. Preferably, the invention utilizes the self-organization process described in copending U.S. patent application Ser. No. 07/915,433, filed Jul. 17, 1992, titled “METHOD AND APPARATUS FOR IMPLEMENTING SELF-ORGANIZATION IN A WIRELESS LOCAL AREA NETWORK.”
FIGS. 2A and 2B generally illustrate the handoff process in a wireless LAN. FIGS. 2A and 2B show a node 20 traveling from one BSA to another. Initially, node 20 is associated with an access point 21. As node 20 moves away from AP 21 and towards AP 22, the quality of the radio link between AP 21 and node 20 deteriorates. Thus, it is desirable to sever the link between node 20 and AP 21, and reassociate node 20 with an AP that would offer a higher quality of message transmission to node 20.
As node 20 approaches the cell occupied by access point 22, AP 22 becomes a potential candidate for reassociation because it is now closer to node 20, and thus is likely to offer a better communications link to the node. Therefore, node 20 is handed off to AP 22, as shown in FIG. 2B.
FIG. 3A is a flow chart illustrating the method of the present invention. In this and other flowcharts herein, the flowchart steps are annotated with the names of the components (shown in FIG. 6) that perform the diagrammed steps. To initiate the process, the node first determines whether handoff is necessary, as shown in step 30 and further illustrated as step 74 in FIG. 3B. For example, the node may measure the quality of the signal received from the access point with which it is communicating, and determine that handoff is necessary when received signal quality drops below a predetermined threshold. In one embodiment, the determination by the node of whether a handoff is necessary may be made in response to a request from the access point with which the node is currently communicating, as shown in FIG. 3C. The current access point communicates a request to the node that it initiate the reassociation process in order to be handed off to another access point, step 37. The node has the option of accepting or rejecting this request, step 38. In another variation, the determination of whether handoff is necessary may be made solely by the current access point. These latter two approaches are useful in the case that the current access point is associated with so many nodes that the traffic of messages communicated through the access point is exceeding its maximum predetermined load, even though the radio link between the node and the access point may be adequate.
When handoff is deemed necessary, the node acquires parameters from other access points. These parameters may include, for example, information concerning administrative domain and access point load. (The administrative domain represents the particular authority which operates a given access point.) Based upon this information and the quality of the signals received from the other access points, the node determines an AP to select for reassociation, step 31.
The selection of the new access point by the node represents a significant advantage over prior art systems in which the node does not actively participate in the reassociation process. In conventional systems, the access points must determine, through communications among themselves, which AP will be associated with the node for handoff, using such criteria as which AP receives the highest quality signal from the node. However, due to the asymmetric nature of radio links, the node itself can best determine the quality of the signal received at the node. Thus, by accounting for the signal reception at the node, the present invention achieves a substantial improvement in the quality of the node-access point association.
After selecting a new access point, the node communicates an instruction to the current access point instructing it to relay a message to the selected access point, requesting that the selected access point accept the handoff of the node, step 32. This request is relayed to the selected access point by the current access point, along with a transfer of certain node parameters representing characteristics of the node, step 33. These node parameters may include, for example, an identification of the user occupying the node.
Under one approach, the selected access point responds automatically to the node's request by transferring a packet containing its operating parameters to the node through the old access point. The operating parameters typically include, but are not limited to, the frequency of the channel on which the selected access point communicates with nodes, spreading codes (in spread spectrum systems) and data encryption information required to access the selected access point. A typical packet is illustrated in FIG. 7. Based upon these access point parameters, the node adjusts its own parameters and commences communication with the new access point, thereby accomplishing handoff, step 35. The process is further illustrated in steps 90, 92 and 94 of FIG. 3D.
Alternatively, the selected access point does not automatically transfer its operating parameters in response to the request of the node. Rather, the selected access point determines whether to accept the handoff based upon predetermined criteria, including the node parameters, step 34. For example, the selected access point may examine whether its load is light enough to accommodate communication with another node, whether the quality of the signal received from the node is satisfactory, and whether the identification of the node reveals that it is authorized to communicate with the selected access point. If the selected access point accepts the handoff, then it transmits its operating parameters to the node through the old AP, so that handoff may be accomplished, step 35.
If, at step 34, the selected access point rejects the request of the node, then the node repeats the reassociation process, steps 31, 32, 33, 34, to select a different access point with which to establish communications.
After handoff has been accomplished, messages intended for the node must be rerouted to the new access point in order to maintain connectivity of the node with the rest of the network. As shown in FIG. 4, in a conventional cellular telephone system, the system may be reconfigured at every point in the communication path in order to reroute a message from its source node 51 to the access point 52 that has accepted handoff of the node 53 from the previous access point 54. As discussed above, this conventional method is too slow to accommodate the handoff of a node that may be engaged in multiple conversations with other nodes.
In contrast, the present invention avoids this degree of complexity. This is illustrated by FIG. 5. Instead of reconfiguring in advance every point throughout the path, the communication path remains intact except that the message is now forwarded from the old access point 61 to the new access point 62. For example, when a message intended for the node 60 is received at access point 61, AP 61 forwards the message to the new access point 62. In this manner, the invention establishes connectivity of the node with network through the second access point, step 36 further illustrated as step 70 in FIG. 3E).
In addition, the old access point 61 may inform other nodes and access points that node 60 is now associated with new access point 62, thus allowing the other access points to adjust their parameters and communicate directly with access point 62 (step 36, further illustrated as step 72 in FIG. 3F). This process of informing other nodes and access points may be performed at a time convenient to do so, i.e., when there is a break in communications and need not be done immediately.
By avoiding reconfiguration of the network at every point in the communication path, the present invention achieves a significant advantage over conventional systems. As discussed above, the conventional method is too slow to accommodate the handoff of a node that may be engaged in multiple conversations with other nodes. However, the manner in which the present invention establishes connectivity between the node through the new access point and the rest of the network is much simpler and faster than the full scale reconfiguration required by conventional means.
FIG. 6 is a simplified block diagram of a node 70 and two access points 74 and 78, which may be used to implement the present invention.
Each node 70 includes a node processing unit 71 which communicates with a device 72 and is connected to an antenna 73 to permit communication between the node and the network. The device 72 represents any apparatus that occupies a node, e.g., a computer, a peripheral device or communications hardware.
Access point 74 includes an AP processing unit 75, which is linked to antenna 76 to allow AP 74 to communicate with node 70 and other nodes in the network.
All communications among access points are handled through AP link 77, which may be implemented as a radio transceiver or as an interface to a separate wired network of access points.
Through AP link 77, access point 74 is connected to other access points, such as access point 78. Access point 78, like access point 74, includes an AP processing unit 79 connected to AP link 77 and an antenna 80.
The node processing unit 71, through antenna 73, communicates via radio with first access point processing unit 75 through antenna 76. The node processing unit 71 may decide that the node 70 should establish communications with another access point if, for example, the quality of signal received by the node processing 71 from the first access point 74 falls below a predetermined signal quality threshold, or if the traffic load being carried by the first access point processing unit 75 exceeds a predetermined load threshold. When handoff is deemed necessary, the node processing unit 71 acquires parameters from other access points. For example, second access point processing unit 79, through antenna 80, may transmit information regarding administrative domain and access point load. Based upon this information and the quality of the signals received from the other access points, the node processing unit 71 selects an AP, such as second access point 78, for reassociation.
After selecting an AP, the node processing unit 71 communicates an instruction to first access point processing unit 75 to relay a request over AP link 77 to second access point processing unit 79, requesting that second access point 78 accept a handoff of the node 70. The request is relayed to second access point processing unit 79 along with a transfer of certain node parameters representing characteristics of the node 70.
Based upon a number of factors, including the node parameters, the AP processing unit 79 determines whether to accept the handoff. If so, then through AP link 77, second access point processing unit 79 transmits operating parameters across AP link 77 to first access point processing unit 75 to be relayed to the node 70. The node processing unit 71 adjusts the operating parameters of the node so that it can communicate across a radio link through antennas 73 and 80 to the second access point processing unit 79, thereby accomplishing handoff.
To maintain connectivity of the node 70 with the rest of the network after handoff, the first access point processing unit 75 forwards messages intended for node 70 across AP link 77 to the second access point processing unit 79 upon receipt of those messages at the first access point 74. In addition, the first access point processing unit 75 may inform other access points over AP link 77 that node 70 is now associated with second access point 78, thus allowing the other access points to communicate directly with access point 78.
Although the invention has been described in conjunction with the preferred embodiment, it will be appreciated that various modifications and alterations might be made by those skilled in the art without departing from the spirit and scope of the invention.

Claims (21)

What is claimed is:
1. In a wireless local area network (LAN) comprising a plurality of cells, each cell including at least one access point for communicating information between cells and at least one node for communicating via the LAN through said access points, a method for maintaining connectivity of a node in the wireless LAN comprising the steps of:
(a) the node selecting a second access point as a candidate for accepting a handoff of the node from a first access point;
(b) communicating an instruction from the node to the first access point instructing the first access point to relay a request to the second access point that the second access point accept a handoff of the node from the first access point to the second access point;
(c) directly relaying said request from the first access point to the second access point; and
(d) performing the handoff, such that the node communicates with the second access point.
2. The method as set forth in claim 1, further comprising the step of determining whether said second access point will accept the request for a handoff.
3. The method as set forth in claim 2, further comprising the step of repeating said selecting, communicating, relaying and determining steps if said second access point determines not to accept said request for a handoff.
4. The method as set forth in claim 1, wherein the step of performing a handoff comprises the steps of:
(a) transmitting second access point operating parameters from said second access point to said first access point;
(b) relaying said second access point operating parameters to said node from said first access point; and
(c) adjusting node parameters in response to said second access point parameters so as to establish communication between said node and said second access point.
5. The method as set forth in claim 4, wherein one of said second access point operating parameters comprises a spreading code utilized by said second access point.
6. The method as set forth in claim 1, further comprising the step of, after said handoff has been performed, forwarding a message that is destined for said node from said first access point to said second access point upon receipt of said message at said first access point, wherein the second access point communicates the message to the node.
7. The method as set forth in claim 1, further comprising the step of, after said handoff has been performed, informing other access points that said node has been handed off to said second access point, such that communications to said node are achieved through said second access point.
8. The method as set forth in claim 1, before said selection step, further comprising the step of the node determining whether to establish connectivity with another access point.
9. The method as set forth in claim 8, further comprising the steps of:
communicating a handoff initiation message from said first access point to said node requesting that said node establish connectivity with another access point; and
said node determining whether to establish connectivity with another access point in response to the request of the first access point.
10. The method as set forth in claim 1, before said selection step, further comprising the step of the first access point determining whether the node should establish connectivity with another access point.
11. In a wireless local area network (LAN) comprising a plurality of cells, each cell including at least one access point for communicating information between cells and at least one node for communicating via the LAN through said access points, a method for maintaining connectivity of a node in the wireless LAN comprising the steps of:
said node determining whether to establish connectivity with another access point; and
if said node determines to establish connectivity with another access point:
said node selecting a second access point as a candidate for accepting a handoff of said node from a first access point;
communicating an instruction from said node to said first access point instructing said first access point to relay a request to said second access point that said second access point accept a handoff of said node from said first access point to said second access point;
relaying said request directly from said first access point to said second access point;
determining whether said second access point will accept said handoff;
if said second access point determines to accept said handoff:
transmitting second access point operating parameters from said second access point to said first access point, wherein one of said operating parameters comprises a spreading code utilized by said second access point;
relaying said second access point operating parameters to said node from said first access point;
adjusting node parameters in response to said second access point operating parameters so as to establish communication between said node and said second access point, thereby accomplishing a handoff; and
if said second access point determines not to accept said handoff, repeating said selecting, communicating, relaying and determining steps.
12. In a wireless local area network (LAN) comprising a plurality of cells, an apparatus for maintaining connectivity in the LAN comprising:
a plurality of access points for communicating information between cells;
link means connected to first and second access points for permitting communications between said first and second access points; and
at least one node for communicating over the LAN through said access points;
each node comprising:
node programming logic for
selecting a second access point as a candidate for handoff of said node from a first access point,
forming an instruction instructing said first access point to relay a request to said second access point requesting that said second access point accept a handoff of said node from said first access point, and causing said instruction to be communicated to said first access point, and
handing off said node to said second access point by establishing communications between said node and said second access point,
said first access point comprising first access point programming logic for relaying said request directly from said first access point to said second access point over said link means.
13. The apparatus as set forth in claim 12, wherein said second access point comprises second access point programming logic for determining whether said second access point will accept said handoff.
14. The apparatus as set forth in claim 13, wherein, if said second access point programming logic determines to reject said handoff, said node programming logic selects an alternate access point and communicates an instruction to the first access point instructing the first access point to relay a request to the alternate access point requesting that the alternate access point accept a handoff of the node.
15. The apparatus as set forth in claim 12, wherein:
said second access point comprises circuitry for relaying second access point operating parameters to said node through said link means and said first access point; and
said node programming logic comprises circuitry for adjusting node parameters in response to said second access point operating parameters so as to establish communications between said node and said second access point.
16. The apparatus as set forth in claim 15, wherein one of said second access point operating parameters comprises a spreading code utilized by said second access point.
17. The apparatus as set forth in claim 12, said first access point further comprising programming logic for forwarding a message that is destined for said node from said first access point to said second access point upon receipt of said message at said first access point.
18. The apparatus as set forth in claim 12, said first access point further comprising programming logic for informing other access points that said node has been handed off to said second access point, such that communications to said node are achieved directly through said second access point.
19. The apparatus as set forth in claim 12, wherein said node further comprises programming logic for determining whether said node will establish connectivity with another access point.
20. The apparatus as set forth in claim 19, wherein
said first access point further comprises programming logic for communicating a handoff initiation message from said first access point to said node requesting that said node establish connectivity with another access point, and
said programming logic for determining whether said node will establish connectivity further comprises programming logic for determining whether said node will establish connectivity with another access point in response to the request of the first access point.
21. The apparatus of claim 19, wherein said first access point further comprises programming logic for determining whether the node should establish connectivity with another access point.
US08/537,408 1992-09-08 1995-10-02 Method and apparatus for maintaining connectivity of nodes in a wireless local area network Expired - Lifetime US6360264B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US08/537,408 US6360264B1 (en) 1992-09-08 1995-10-02 Method and apparatus for maintaining connectivity of nodes in a wireless local area network

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US94173592A 1992-09-08 1992-09-08
US31607894A 1994-09-30 1994-09-30
US08/537,408 US6360264B1 (en) 1992-09-08 1995-10-02 Method and apparatus for maintaining connectivity of nodes in a wireless local area network

Related Parent Applications (1)

Application Number Title Priority Date Filing Date
US31607894A Continuation 1992-09-08 1994-09-30

Publications (1)

Publication Number Publication Date
US6360264B1 true US6360264B1 (en) 2002-03-19

Family

ID=25476988

Family Applications (1)

Application Number Title Priority Date Filing Date
US08/537,408 Expired - Lifetime US6360264B1 (en) 1992-09-08 1995-10-02 Method and apparatus for maintaining connectivity of nodes in a wireless local area network

Country Status (5)

Country Link
US (1) US6360264B1 (en)
EP (1) EP0589552B1 (en)
JP (1) JP3412639B2 (en)
KR (1) KR100289631B1 (en)
DE (1) DE69332431T2 (en)

Cited By (45)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6492897B1 (en) 2000-08-04 2002-12-10 Richard A. Mowery, Jr. System for coupling wireless signals to and from a power transmission line communication system
US20030185172A1 (en) * 2002-03-27 2003-10-02 Seon-Soo Rue Apparatus and method for supporting mobility between subnetworks of mobile node in wireless LAN
US6636491B1 (en) * 1998-01-14 2003-10-21 Nokia Corporation Access control method for a mobile communications system
WO2003100990A2 (en) * 2002-05-23 2003-12-04 Nokia Corporation Method and system for access point roaming
US6671737B1 (en) * 1999-09-24 2003-12-30 Xerox Corporation Decentralized network system
US20040014422A1 (en) * 2002-07-19 2004-01-22 Nokia Corporation Method and system for handovers using service description data
US20040053624A1 (en) * 2002-09-17 2004-03-18 Frank Ed H. Method and system for optimal load balancing in a hybrid wired/wireless network
US20040095924A1 (en) * 2002-11-18 2004-05-20 Holur Balaji S. Method and system for voice calls in a wireless local area network (WLAN)
US20040196808A1 (en) * 2001-06-28 2004-10-07 Chaskar Hemant M. Protocol to determine optimal target access routers for seamless IP-level handover
US20040203783A1 (en) * 2002-11-08 2004-10-14 Gang Wu Wireless network handoff key
US20040224690A1 (en) * 2003-01-23 2004-11-11 Samsung Electronics Co., Ltd. Handoff method in wireless LAN, and access point and mobile station performing handoff method
US20040236939A1 (en) * 2003-02-20 2004-11-25 Docomo Communications Laboratories Usa, Inc. Wireless network handoff key
US20050013276A1 (en) * 2003-07-17 2005-01-20 Ekl Randy L. Method for performing a seamless handoff in a communication system
WO2005011182A2 (en) * 2003-07-22 2005-02-03 Pctel, Inc. Method and apparatus for automatic configuration of wireless networks
US20050083887A1 (en) * 2002-11-08 2005-04-21 Samsung Electronics Co., Ltd. Method for performing handoff in wireless network
US20050130658A1 (en) * 2003-12-15 2005-06-16 Intel Corporation Handoff apparatus, systems, and methods
US20050198337A1 (en) * 2004-01-26 2005-09-08 Nortel Networks Limited Multiple simultaneous wireless connections in a wireless local area network
US6961774B1 (en) * 2001-08-02 2005-11-01 Cisco Technology, Inc. System and method for performing hand-offs between internet protocol (IP) core networks in the wireless domain
US20050259619A1 (en) * 2004-05-24 2005-11-24 Alcatel Cellular broadband wireless access network for a railway
US20060056348A1 (en) * 2004-09-10 2006-03-16 Interdigital Technology Corporation Wireless communication methods and components that implement handoff in wireless local area networks
US20060062183A1 (en) * 2004-03-03 2006-03-23 Forte Andrea G Methods and systems for reducing MAC layer handoff latency in wireless networks
US20060084439A1 (en) * 2004-10-15 2006-04-20 Avinash Joshi System and method to facilitate inter-frequency handoff of mobile terminals in a wireless communication network
US7039674B1 (en) * 1999-07-14 2006-05-02 Samsung Electronics Co., Ltd Method of changing program of network node remote from network management system
WO2005122607A3 (en) * 2004-06-07 2006-07-06 Nokia Inc Method and system for enhanced capacity and quality over wlan
US20060245399A1 (en) * 2002-11-18 2006-11-02 Cisco Technology, Inc. Method and system for service portability across disjoint wireless networks
US20070025293A1 (en) * 2005-07-27 2007-02-01 Samsung Electronics Co., Ltd. Method and mobile device for performing fast hand-over in WLAN and method of switching services using GPS information
US20070047492A1 (en) * 2005-08-29 2007-03-01 Samsung Electronics Co., Ltd. Method and apparatus for fast and efficient handover at link layer of wireless LAN
US20070053362A1 (en) * 2003-08-01 2007-03-08 Koninklijke Philips Electronics N.V. Bss-switch module for wireless devices
US20070064660A1 (en) * 2005-09-16 2007-03-22 Qi Emily H Techniques for enhanced transition from access point to access point by a mobile wireless device
US20070192489A1 (en) * 2006-02-14 2007-08-16 Motorola, Inc. Method and apparatus to facilitate automatic selection of sotware programs to be distributed to network elements
US20070236345A1 (en) * 2006-04-05 2007-10-11 Motorola, Inc. Wireless sensor node executable code request facilitation method and apparatus
US7283505B1 (en) * 2002-10-31 2007-10-16 Aol Llc, A Delaware Limited Liability Company Configuring wireless access points
US20070266078A1 (en) * 2006-04-05 2007-11-15 Motorola, Inc. Wireless sensor node group affiliation method and apparatus
US7313384B1 (en) 2002-10-31 2007-12-25 Aol Llc, A Delaware Limited Liability Company Configuring wireless devices
US20090037570A1 (en) * 2007-08-01 2009-02-05 Motorola, Inc. Method and Apparatus for Resource Assignment in a Sensor Network
US20100014483A1 (en) * 2006-06-23 2010-01-21 Robert Hancock Network Selection
US7752329B1 (en) 2002-10-31 2010-07-06 Aol Inc. Migrating configuration information based on user identity information
WO2011126883A3 (en) * 2010-03-30 2011-12-08 Qualcomm Incorporated Methods and apparatus for service continuity in a communication network
US20120093066A1 (en) * 2009-04-27 2012-04-19 Ntt Docomo, Inc. Mobile communication system
US20130005391A1 (en) * 2011-06-30 2013-01-03 Motorola Solutions, Inc. Methods for intelligent network selection
CN101390407B (en) * 2004-09-10 2013-01-23 美商内数位科技公司 Wireless communication methods and components that implement handoff in wireless local area networks
US8631368B2 (en) 2010-03-30 2014-01-14 Qualcomm Incorporated Method and circuit to generate race condition test data at multiple supply voltages
US20150172988A1 (en) * 2013-12-18 2015-06-18 Telefonaktiebolaget L M Erisson (Publ) Reduced wireless communication handover command size during handover execution
US20150312131A1 (en) * 2014-04-29 2015-10-29 Aruba Networks, Inc. Software Defined Wireless Device Management
US10116626B2 (en) 2013-06-05 2018-10-30 Fortinet, Inc. Cloud based logging service

Families Citing this family (27)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6088591A (en) * 1996-06-28 2000-07-11 Aironet Wireless Communications, Inc. Cellular system hand-off protocol
FI103162B (en) 1996-12-20 1999-04-30 Nokia Mobile Phones Ltd Network design for the creation of a wireless ATM system part and method for performing a handover between switches in such a network design
CA2221948A1 (en) * 1996-12-30 1998-06-30 Lucent Technologies Inc. System and method for achieving handover in wireless lan by buffering data at subsequent access point
US6044271A (en) * 1997-12-23 2000-03-28 Ericsson Inc. System and method for handing off a cellular call with system and capability change indication
DE19834634C2 (en) * 1998-07-31 2002-06-20 Siemens Ag Communication arrangement with at least one central communication device to which wireless network termination devices can be connected for the connection of communication terminals
WO2001047298A2 (en) * 1999-12-13 2001-06-28 Ericsson Inc. Fast cell re-selection for real time packet data networks
EP1139606A1 (en) * 2000-03-28 2001-10-04 Lucent Technologies Inc. Wireless communication in a lan with varying signal level thresholds
GB0023425D0 (en) * 2000-09-25 2000-11-08 Koninkl Philips Electronics Nv Portable device interaction with beacons
KR100431471B1 (en) * 2001-09-04 2004-05-14 아이피원(주) An internet service system using sectorizated wireless LAN, and its handover and roaming method among sectors
EP1292073A1 (en) * 2001-09-05 2003-03-12 Z-Com, Inc. Method for connecting the access points of two wireless local area networks
KR100463067B1 (en) * 2001-12-29 2004-12-23 하나로통신 주식회사 Method for hand-off in access network of based wireless LAN
KR20020023918A (en) * 2001-12-29 2002-03-29 박재홍 Method for hand-off using beacon message in based wireless LAN
KR20030063502A (en) * 2002-01-22 2003-07-31 프로모바일테크 주식회사 Wireless LAN System for prcessing Internet service roaming of mobile device and method thereof
US6990342B2 (en) * 2002-08-29 2006-01-24 Motorola, Inx. Method and apparatus for cell reselection within a communications system
TWI353753B (en) 2003-03-27 2011-12-01 Lenovo Singapore Pte Ltd Access to a wireless local area network
GB2409377B (en) 2003-12-17 2006-05-24 Motorola Inc Wireless access networks
US20050135310A1 (en) * 2003-12-19 2005-06-23 International Business Machines Corporation Autonomic client reassociation in a wireless local area network
FR2898009A1 (en) * 2006-02-27 2007-08-31 France Telecom Network e.g. Internet, access point and wireless terminal communicating method for e.g. voice over internet Protocol application, involves transmitting roaming probe response message to wireless terminal over radio channel via access point
EP2015591B1 (en) * 2006-04-28 2018-10-10 Panasonic Intellectual Property Corporation of America Communication terminal apparatus and handover method
US20090137228A1 (en) * 2007-11-16 2009-05-28 Qualcomm Incorporated Utilizing restriction codes in wireless access point connection attempts
US8848656B2 (en) 2007-11-16 2014-09-30 Qualcomm Incorporated Utilizing broadcast signals to convey restricted association information
US8737295B2 (en) 2007-11-16 2014-05-27 Qualcomm Incorporated Sector identification using sector parameters signatures
US9603062B2 (en) 2007-11-16 2017-03-21 Qualcomm Incorporated Classifying access points using pilot identifiers
US8902867B2 (en) 2007-11-16 2014-12-02 Qualcomm Incorporated Favoring access points in wireless communications
WO2009067637A1 (en) 2007-11-21 2009-05-28 Nortel Networks Limited Computing an action time for allocation of resources to a mobile station that is handing over from a source to a target base station
US8588773B2 (en) 2008-08-04 2013-11-19 Qualcomm Incorporated System and method for cell search and selection in a wireless communication system
US10820266B2 (en) 2018-04-13 2020-10-27 Cisco Technology, Inc. Method and device for dynamic and seamless link selection

Citations (22)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4549302A (en) * 1981-06-15 1985-10-22 Hayes Microcomputer Products, Inc. Modem with improved escape sequence mechanism to prevent escape in response to random occurrence of escape character in transmitted data
US4718081A (en) * 1986-11-13 1988-01-05 General Electric Company Method and apparatus for reducing handoff errors in a cellular radio telephone communications system
US4765753A (en) * 1986-03-08 1988-08-23 U.S. Philips Corporation Method and apparatus for handing-over a radio connection from one radio cell to another radio cell of a digital radio transmission system
US4783780A (en) * 1985-07-09 1988-11-08 U.S. Philips Corp. Method and apparatus for selecting a free channel in a mobile radio system
US4797947A (en) * 1987-05-01 1989-01-10 Motorola, Inc. Microcellular communications system using macrodiversity
US4881271A (en) * 1987-03-20 1989-11-14 Hitachi, Ltd. Portable wireless communication systems
US4907290A (en) 1987-05-15 1990-03-06 Datatrak Limited Mobile transmitter/receiver
EP0364638A1 (en) 1988-10-20 1990-04-25 International Business Machines Corporation Communication network
US4958341A (en) 1988-03-31 1990-09-18 At&T Bell Laboratories Integrated packetized voice and data switching system
WO1991007020A1 (en) * 1989-11-07 1991-05-16 Qualcomm Incorporated Soft handoff in a cdma cellular telephone system
US5042082A (en) * 1989-06-26 1991-08-20 Telefonaktiebolaget L. M. Ericsson Mobile assisted handoff
US5068916A (en) 1990-10-29 1991-11-26 International Business Machines Corporation Coordination of wireless medium among a plurality of base stations
EP0483544A1 (en) 1990-10-29 1992-05-06 International Business Machines Corporation Distributed control methods for management of migrating data stations in a wireless communications network
EP0483551A2 (en) 1990-10-29 1992-05-06 International Business Machines Corporation Handoff method and apparatus for mobile wireless workstations
US5119397A (en) 1990-04-26 1992-06-02 Telefonaktiebolaget L M Ericsson Combined analog and digital cellular telephone system having a secondary set of control channels
US5123029A (en) 1991-06-21 1992-06-16 International Business Machines Corporation Broadcast-initiated bipartite frame multi-access protocol
US5179559A (en) * 1990-07-27 1993-01-12 Motorola, Inc. Handoff method for a cellular system
US5199031A (en) 1990-08-31 1993-03-30 Telefonaktiebolaget L M Ericsson Method and system for uniquely identifying control channel time slots
US5222249A (en) * 1990-11-08 1993-06-22 Motorola, Inc. Dynamic rf communication resource access by roving mobile units
US5321542A (en) 1990-10-29 1994-06-14 International Business Machines Corporation Control method and apparatus for wireless data link
US5323446A (en) * 1991-04-17 1994-06-21 Nec Corporation Digital cellular switching system with means for securing uninterrupted data transparency during handoffs
US5408514A (en) * 1990-10-02 1995-04-18 Nippon Telegraph And Telephone Corporation Method of handover and route diversity in mobile radio communication

Patent Citations (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4549302A (en) * 1981-06-15 1985-10-22 Hayes Microcomputer Products, Inc. Modem with improved escape sequence mechanism to prevent escape in response to random occurrence of escape character in transmitted data
US4783780A (en) * 1985-07-09 1988-11-08 U.S. Philips Corp. Method and apparatus for selecting a free channel in a mobile radio system
US4765753A (en) * 1986-03-08 1988-08-23 U.S. Philips Corporation Method and apparatus for handing-over a radio connection from one radio cell to another radio cell of a digital radio transmission system
US4718081A (en) * 1986-11-13 1988-01-05 General Electric Company Method and apparatus for reducing handoff errors in a cellular radio telephone communications system
US4881271A (en) * 1987-03-20 1989-11-14 Hitachi, Ltd. Portable wireless communication systems
US4797947A (en) * 1987-05-01 1989-01-10 Motorola, Inc. Microcellular communications system using macrodiversity
US4907290A (en) 1987-05-15 1990-03-06 Datatrak Limited Mobile transmitter/receiver
US4958341A (en) 1988-03-31 1990-09-18 At&T Bell Laboratories Integrated packetized voice and data switching system
EP0364638A1 (en) 1988-10-20 1990-04-25 International Business Machines Corporation Communication network
US5042082A (en) * 1989-06-26 1991-08-20 Telefonaktiebolaget L. M. Ericsson Mobile assisted handoff
WO1991007020A1 (en) * 1989-11-07 1991-05-16 Qualcomm Incorporated Soft handoff in a cdma cellular telephone system
US5119397A (en) 1990-04-26 1992-06-02 Telefonaktiebolaget L M Ericsson Combined analog and digital cellular telephone system having a secondary set of control channels
US5179559A (en) * 1990-07-27 1993-01-12 Motorola, Inc. Handoff method for a cellular system
US5199031A (en) 1990-08-31 1993-03-30 Telefonaktiebolaget L M Ericsson Method and system for uniquely identifying control channel time slots
US5408514A (en) * 1990-10-02 1995-04-18 Nippon Telegraph And Telephone Corporation Method of handover and route diversity in mobile radio communication
EP0483551A2 (en) 1990-10-29 1992-05-06 International Business Machines Corporation Handoff method and apparatus for mobile wireless workstations
US5181200A (en) * 1990-10-29 1993-01-19 International Business Machines Corporation Handoff method and apparatus for mobile wireless workstation
EP0483544A1 (en) 1990-10-29 1992-05-06 International Business Machines Corporation Distributed control methods for management of migrating data stations in a wireless communications network
US5321542A (en) 1990-10-29 1994-06-14 International Business Machines Corporation Control method and apparatus for wireless data link
US5068916A (en) 1990-10-29 1991-11-26 International Business Machines Corporation Coordination of wireless medium among a plurality of base stations
US5222249A (en) * 1990-11-08 1993-06-22 Motorola, Inc. Dynamic rf communication resource access by roving mobile units
US5323446A (en) * 1991-04-17 1994-06-21 Nec Corporation Digital cellular switching system with means for securing uninterrupted data transparency during handoffs
US5123029A (en) 1991-06-21 1992-06-16 International Business Machines Corporation Broadcast-initiated bipartite frame multi-access protocol

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
11th Annual International Phoenix Conference on Computer and Communications Apr. 1, 1992, Scottsdale, US, pp. 255-259, XP310617 K.Arai et al "A Hybrid Indoor Data Network With Radio And Wire Performance Evaluation In A Rayleigh Channel' *the whole document*.
11th Annual International Phoenix Conference on Computer and Communications Apr. 1, 1992, Scottsdale, US, pp. 255-259, XP310617 K.Arai et al ‘A Hybrid Indoor Data Network With Radio And Wire Performance Evaluation In A Rayleigh Channel’ *the whole document*.
R.E. Kahn et al; "Advances in Packet Radio Technology"; Proceeding of the IEEE; vol. 66, No. 11, Nov. 1978, pp. 1468-1496.*

Cited By (107)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6636491B1 (en) * 1998-01-14 2003-10-21 Nokia Corporation Access control method for a mobile communications system
US7039674B1 (en) * 1999-07-14 2006-05-02 Samsung Electronics Co., Ltd Method of changing program of network node remote from network management system
US6671737B1 (en) * 1999-09-24 2003-12-30 Xerox Corporation Decentralized network system
US6492897B1 (en) 2000-08-04 2002-12-10 Richard A. Mowery, Jr. System for coupling wireless signals to and from a power transmission line communication system
US7480307B2 (en) * 2001-06-28 2009-01-20 Nokia, Inc. Protocol to determine optimal target access routers for seamless IP-level handover
US7313628B2 (en) * 2001-06-28 2007-12-25 Nokia, Inc. Protocol to determine optimal target access routers for seamless IP-level handover
US20050100030A1 (en) * 2001-06-28 2005-05-12 Nokia, Inc. Protocol to determine optimal target access routers for seamless IP-level handover
US8804712B2 (en) * 2001-06-28 2014-08-12 Nokia, Inc. Determining target access routers for handover
US20050105491A1 (en) * 2001-06-28 2005-05-19 Nokia, Inc. Protocol to determine optimal target access routers for seamless IP-level handover
US20040196808A1 (en) * 2001-06-28 2004-10-07 Chaskar Hemant M. Protocol to determine optimal target access routers for seamless IP-level handover
US6961774B1 (en) * 2001-08-02 2005-11-01 Cisco Technology, Inc. System and method for performing hand-offs between internet protocol (IP) core networks in the wireless domain
US20030185172A1 (en) * 2002-03-27 2003-10-02 Seon-Soo Rue Apparatus and method for supporting mobility between subnetworks of mobile node in wireless LAN
US7450544B2 (en) 2002-03-27 2008-11-11 Samsung Electronics Co., Ltd. Apparatus and method for supporting mobility between subnetworks of mobile node in wireless LAN
WO2003100990A2 (en) * 2002-05-23 2003-12-04 Nokia Corporation Method and system for access point roaming
US7103359B1 (en) 2002-05-23 2006-09-05 Nokia Corporation Method and system for access point roaming
WO2003100990A3 (en) * 2002-05-23 2004-02-26 Nokia Corp Method and system for access point roaming
US20040014422A1 (en) * 2002-07-19 2004-01-22 Nokia Corporation Method and system for handovers using service description data
US20040053624A1 (en) * 2002-09-17 2004-03-18 Frank Ed H. Method and system for optimal load balancing in a hybrid wired/wireless network
US7653379B1 (en) 2002-10-31 2010-01-26 Aol Llc Configuring wireless devices
US7313384B1 (en) 2002-10-31 2007-12-25 Aol Llc, A Delaware Limited Liability Company Configuring wireless devices
US7752329B1 (en) 2002-10-31 2010-07-06 Aol Inc. Migrating configuration information based on user identity information
US20100257584A1 (en) * 2002-10-31 2010-10-07 Aol Inc. Migrating Configuration Information Based on User Identity Information
US8275900B2 (en) 2002-10-31 2012-09-25 Aol Inc. Migrating configuration information based on user identity information
US7986938B1 (en) 2002-10-31 2011-07-26 Aol Inc. Configuring wireless devices
US9553738B2 (en) 2002-10-31 2017-01-24 Aol Inc. Migrating configuration information based on user identity information
US7283505B1 (en) * 2002-10-31 2007-10-16 Aol Llc, A Delaware Limited Liability Company Configuring wireless access points
US7792527B2 (en) * 2002-11-08 2010-09-07 Ntt Docomo, Inc. Wireless network handoff key
US20050143073A1 (en) * 2002-11-08 2005-06-30 Samsung Electronics Co., Ltd. Method for performing handoff in wireless network
US20050083887A1 (en) * 2002-11-08 2005-04-21 Samsung Electronics Co., Ltd. Method for performing handoff in wireless network
US20040203783A1 (en) * 2002-11-08 2004-10-14 Gang Wu Wireless network handoff key
US8977265B2 (en) * 2002-11-08 2015-03-10 Samsung Electronics Co., Ltd. Method for performing handoff in wireless network
US7079521B2 (en) 2002-11-18 2006-07-18 Cisco Technology, Inc. Method and system for voice calls in a wireless local area network (WLAN)
US20060245399A1 (en) * 2002-11-18 2006-11-02 Cisco Technology, Inc. Method and system for service portability across disjoint wireless networks
US7826433B2 (en) 2002-11-18 2010-11-02 Cisco Technology, Inc. Method and system for voice calls in a wireless local area network (WLAN)
US20040095924A1 (en) * 2002-11-18 2004-05-20 Holur Balaji S. Method and system for voice calls in a wireless local area network (WLAN)
US9814086B2 (en) 2002-11-18 2017-11-07 Cisco Technology, Inc. Method and system for service portability across disjoint wireless networks
US20060198365A1 (en) * 2002-11-18 2006-09-07 Cisco Technology, Inc. Method and System for Voice Calls in a Wireless Local Area Network (WLAN)
US8374148B2 (en) * 2003-01-23 2013-02-12 Samsung Electronics Co., Ltd. Handoff method in wireless LAN, and access point and mobile station performing handoff method
US20040224690A1 (en) * 2003-01-23 2004-11-11 Samsung Electronics Co., Ltd. Handoff method in wireless LAN, and access point and mobile station performing handoff method
US20090175449A1 (en) * 2003-02-20 2009-07-09 Ntt Docomo, Inc. Wireless network handoff key
US20090175448A1 (en) * 2003-02-20 2009-07-09 Fujio Watanabe Wireless network handoff key
US20090208013A1 (en) * 2003-02-20 2009-08-20 Fujio Watanabe Wireless network handoff key
US20040236939A1 (en) * 2003-02-20 2004-11-25 Docomo Communications Laboratories Usa, Inc. Wireless network handoff key
US20090175454A1 (en) * 2003-02-20 2009-07-09 Fujio Watanabe Wireless network handoff key
US7058030B2 (en) * 2003-07-17 2006-06-06 Motorola, Inc. Method for performing a seamless handoff in a communication system
US20050013276A1 (en) * 2003-07-17 2005-01-20 Ekl Randy L. Method for performing a seamless handoff in a communication system
WO2005011182A3 (en) * 2003-07-22 2006-05-04 Pctel Inc Method and apparatus for automatic configuration of wireless networks
WO2005011182A2 (en) * 2003-07-22 2005-02-03 Pctel, Inc. Method and apparatus for automatic configuration of wireless networks
US20050078624A1 (en) * 2003-07-22 2005-04-14 Zhengjin Shu Method and apparatus for automatic configuration of wireless networks
US20070053362A1 (en) * 2003-08-01 2007-03-08 Koninklijke Philips Electronics N.V. Bss-switch module for wireless devices
US7558567B2 (en) * 2003-08-01 2009-07-07 Nxp B.V. BSS-switch module for wireless devices
US7072652B2 (en) * 2003-12-15 2006-07-04 Intel Corporation Handoff apparatus, systems, and methods
US20050130658A1 (en) * 2003-12-15 2005-06-16 Intel Corporation Handoff apparatus, systems, and methods
US20050198337A1 (en) * 2004-01-26 2005-09-08 Nortel Networks Limited Multiple simultaneous wireless connections in a wireless local area network
US7836189B2 (en) * 2004-01-26 2010-11-16 Avaya Inc. Multiple simultaneous wireless connections in a wireless local area network
US8737351B2 (en) 2004-03-03 2014-05-27 The Trustees Of Columbia University In The City Of New York Methods and systems for reducing MAC layer handoff latency in wireless networks
US20060062183A1 (en) * 2004-03-03 2006-03-23 Forte Andrea G Methods and systems for reducing MAC layer handoff latency in wireless networks
US20100135252A1 (en) * 2004-03-03 2010-06-03 The Trustees Of Columbia University In The City Of New York Methods and systems for reducing mac layer handoff latency in wireless networks
US7636336B2 (en) 2004-03-03 2009-12-22 The Trustees Of Columbia University In The City Of New York Methods and systems for reducing MAC layer handoff latency in wireless networks
US20050259619A1 (en) * 2004-05-24 2005-11-24 Alcatel Cellular broadband wireless access network for a railway
WO2005122607A3 (en) * 2004-06-07 2006-07-06 Nokia Inc Method and system for enhanced capacity and quality over wlan
US7894823B2 (en) 2004-06-07 2011-02-22 Nokia Inc. System for enhanced capacity and quality over WLAN
WO2006031588A2 (en) 2004-09-10 2006-03-23 Interdigital Technology Corporation Wireless communication methods and components that implement handoff in wireless local area networks
EP1795017A2 (en) * 2004-09-10 2007-06-13 Interdigital Technology Corporation Wireless communication methods and components that implement handoff in wireless local area networks
US7706326B2 (en) * 2004-09-10 2010-04-27 Interdigital Technology Corporation Wireless communication methods and components that implement handoff in wireless local area networks
US20060056348A1 (en) * 2004-09-10 2006-03-16 Interdigital Technology Corporation Wireless communication methods and components that implement handoff in wireless local area networks
TWI501681B (en) * 2004-09-10 2015-09-21 Interdigital Tech Corp Wireless communication methods and components that implement handoff in wireless local area networks
US20100202409A1 (en) * 2004-09-10 2010-08-12 Interdigital Technology Corporation Wireless communication methods and components that implement handoff in wireless local area networks
AU2005285179B2 (en) * 2004-09-10 2009-09-03 Interdigital Technology Corporation Wireless communication methods and components that implement handoff in wireless local area networks
WO2006031588A3 (en) * 2004-09-10 2006-08-03 Interdigital Tech Corp Wireless communication methods and components that implement handoff in wireless local area networks
EP1795017A4 (en) * 2004-09-10 2007-12-12 Interdigital Tech Corp Wireless communication methods and components that implement handoff in wireless local area networks
US8867487B2 (en) 2004-09-10 2014-10-21 Interdigital Technology Corporation Wireless communication methods and components that implement handoff in wireless local area networks
KR101329368B1 (en) 2004-09-10 2013-11-14 인터디지탈 테크날러지 코포레이션 Wireless communication methods and components that implement handoff in wireless local area networks
KR101289119B1 (en) 2004-09-10 2013-08-07 인터디지탈 테크날러지 코포레이션 Wireless communication methods and components that implement handoff in wireless local area networks
TWI394405B (en) * 2004-09-10 2013-04-21 Interdigital Tech Corp Wireless communication methods and components implement that handoff in wireless local area networks
AU2009243501B2 (en) * 2004-09-10 2013-01-31 Interdigital Technology Corporation Wireless communication methods and components that implement handoff in wireless local area networks
US8027312B2 (en) 2004-09-10 2011-09-27 Interdigital Technology Corporation Wireless communication methods and components that implement handoff in wireless local area networks
CN101390407B (en) * 2004-09-10 2013-01-23 美商内数位科技公司 Wireless communication methods and components that implement handoff in wireless local area networks
KR101221860B1 (en) * 2004-09-10 2013-01-16 인터디지탈 테크날러지 코포레이션 Wireless communication methods and components that implement handoff in wireless local area networks
US7929968B2 (en) 2004-10-15 2011-04-19 Meshnetworks, Inc. System and method to facilitate inter-frequency handoff of mobile terminals in a wireless communication network
US20060084439A1 (en) * 2004-10-15 2006-04-20 Avinash Joshi System and method to facilitate inter-frequency handoff of mobile terminals in a wireless communication network
US8897777B2 (en) * 2005-07-27 2014-11-25 Samsung Electroncis Co., Ltd. Method and mobile device for performing fast hand-over in WLAN and method of switching services using GPS information
US20070025293A1 (en) * 2005-07-27 2007-02-01 Samsung Electronics Co., Ltd. Method and mobile device for performing fast hand-over in WLAN and method of switching services using GPS information
US20070047492A1 (en) * 2005-08-29 2007-03-01 Samsung Electronics Co., Ltd. Method and apparatus for fast and efficient handover at link layer of wireless LAN
US8428028B2 (en) * 2005-08-29 2013-04-23 Samsung Electronics Co., Ltd. Method and apparatus for fast and efficient handover at link layer of wireless LAN
US20070064660A1 (en) * 2005-09-16 2007-03-22 Qi Emily H Techniques for enhanced transition from access point to access point by a mobile wireless device
GB2442907B (en) * 2005-09-16 2010-12-08 Intel Corp Techniques for enhanced transition from access point to access point by a mobile wireless device
US20070192489A1 (en) * 2006-02-14 2007-08-16 Motorola, Inc. Method and apparatus to facilitate automatic selection of sotware programs to be distributed to network elements
US7676805B2 (en) * 2006-04-05 2010-03-09 Motorola, Inc. Wireless sensor node executable code request facilitation method and apparatus
US20070266078A1 (en) * 2006-04-05 2007-11-15 Motorola, Inc. Wireless sensor node group affiliation method and apparatus
US7688793B2 (en) 2006-04-05 2010-03-30 Motorola, Inc. Wireless sensor node group affiliation method and apparatus
US20070236345A1 (en) * 2006-04-05 2007-10-11 Motorola, Inc. Wireless sensor node executable code request facilitation method and apparatus
US9025514B2 (en) 2006-06-23 2015-05-05 Nokia Solutions And Networks Gmbh & Co. Kg Network selection
US8270409B2 (en) * 2006-06-23 2012-09-18 Nokia Siemens Networks Gmbh & Co. Kg Network selection
US20100014483A1 (en) * 2006-06-23 2010-01-21 Robert Hancock Network Selection
US8131839B2 (en) 2007-08-01 2012-03-06 Motorola Solutions, Inc. Method and apparatus for resource assignment in a sensor network
US20090037570A1 (en) * 2007-08-01 2009-02-05 Motorola, Inc. Method and Apparatus for Resource Assignment in a Sensor Network
US20120093066A1 (en) * 2009-04-27 2012-04-19 Ntt Docomo, Inc. Mobile communication system
US8631368B2 (en) 2010-03-30 2014-01-14 Qualcomm Incorporated Method and circuit to generate race condition test data at multiple supply voltages
WO2011126883A3 (en) * 2010-03-30 2011-12-08 Qualcomm Incorporated Methods and apparatus for service continuity in a communication network
US8660097B2 (en) 2010-03-30 2014-02-25 Qualcomm Incorporated Methods and apparatus for service continuity in a communication network
US9148846B2 (en) * 2011-06-30 2015-09-29 Motorola Solutions, Inc. Methods for intelligent network selection
US20130005391A1 (en) * 2011-06-30 2013-01-03 Motorola Solutions, Inc. Methods for intelligent network selection
US10116626B2 (en) 2013-06-05 2018-10-30 Fortinet, Inc. Cloud based logging service
US20150172988A1 (en) * 2013-12-18 2015-06-18 Telefonaktiebolaget L M Erisson (Publ) Reduced wireless communication handover command size during handover execution
US10080166B2 (en) * 2014-04-29 2018-09-18 Hewlett Packard Enterprise Development Lp Software defined wireless device management
US20150312131A1 (en) * 2014-04-29 2015-10-29 Aruba Networks, Inc. Software Defined Wireless Device Management

Also Published As

Publication number Publication date
KR940008311A (en) 1994-04-29
DE69332431T2 (en) 2003-06-18
EP0589552A3 (en) 1995-09-27
KR100289631B1 (en) 2001-05-02
JP3412639B2 (en) 2003-06-03
EP0589552B1 (en) 2002-10-23
DE69332431D1 (en) 2002-11-28
JPH0723042A (en) 1995-01-24
EP0589552A2 (en) 1994-03-30

Similar Documents

Publication Publication Date Title
US6360264B1 (en) Method and apparatus for maintaining connectivity of nodes in a wireless local area network
US5515509A (en) Method and apparatus for implementing self-organization in a wireless local area network
EP1071305B1 (en) Method and apparatus for base station controlled handoff
US5528583A (en) Method and apparatus for supporting mobile communications in mobile communications networks
US6424638B1 (en) System and method for performing an inter mobile system handover using the internet telephony system
US7515568B2 (en) Neighborhood wireless protocol with switchable ad hoc and wide area network coverage
US8958428B2 (en) Method and system for configuring wireless routers and networks
US7454210B2 (en) Control of radio communication network having plural radio network controllers including an anchor controller
US7986660B2 (en) Channel allocation for communication system
US5794149A (en) Base station controlled handoff method and apparatus
US8027312B2 (en) Wireless communication methods and components that implement handoff in wireless local area networks
JP3506331B2 (en) System network and method for transfer of cell handover information
EP2157808B1 (en) Adaptive management method for wireless transfer network containing base station and wireless relay stations
GB2322522A (en) Call set-up method in a radio communication system
CA2346919A1 (en) Method and apparatus for setting up a cordless mobile telecommunications system
JP2006524965A (en) Method and system for integrating resource allocation between TDD and FDD in a wireless communication system
EP3606180B1 (en) A method of securing wireless backhaul, a child base station, a parent base station and methods in the child and parent base stations
US6707803B1 (en) Device and method for performing inter-MSC soft handoff using router in CDMA communication system
MXPA06003302A (en) Method and system for integrating resource allocation between time division duplex and frequency division duplex in wireless communication systems.
US7768974B2 (en) Method and arrangement for generating pilot beacons in wireless communication systems
US6620014B1 (en) Communicating radio planning information among control nodes in a cellular communication network
NO325602B1 (en) Method of controlling load in a communication system
KR19990018250A (en) Handoff Method in Mobile Communication System
MXPA00008533A (en) Telecommunications inter-exchange measurement transfer
KR20000008947A (en) Soft handoff method between mobile switching centers in a cellular systme

Legal Events

Date Code Title Description
STCF Information on status: patent grant

Free format text: PATENTED CASE

FPAY Fee payment

Year of fee payment: 4

FPAY Fee payment

Year of fee payment: 8

FPAY Fee payment

Year of fee payment: 12